04 Accord V6 PCM replacement?
 

A couple of weeks ago I cleaned my K&N air filter and put it back in. The next morning I got in the car and the air blew, just not cold. I took it to a buddy of mine who said the compressor is not engaging and said no voltage coming from the relay. I got a new relay (as well as swapped a few around but nothing changed so I took it to the local (non-dealership) shop who said the ground is not coming from the ECM and they said the ECM needed to be replaced, but the dealership would need to do it as they can reprogram after replacement. They also added that the compressor clutch would need to be replaced. I then had to travel for business and when I got back, the battery was dead, I can jump it and after driving a bit it will restart on its own for several hours but that time is getting smaller.

I then took the car yesterday to the dealership and didn't give them the details and they came back saying the PCM needs to be replaced as well as the compressor clutch and coil. They gave me a quote of around $2300 before trying to get me to buy a new car.

I am fairly handy with cars and have access to many mechanics. My issue is the car is paid off and I really like it. I think $2300 is really high and would like to get suggestions from you guys. It is a 2004 Accord Sedan v6.

I have thought about buying a new PCM and replacing it, but then I would need to program it and I don't seem to have the resources. I can definitely replace the compressor and clutch.

Thanks.
Scott
ciscorbin@yahoo.com

I was speaking to my mechanic friend and I think the battery thing is a separate issue so I am going to have the battery tested tomorrow (Friday).

So no voltage is getting to the compressor due to compressor relay not receiving a ground signal from PCM. Has this been confirmed?

One good reason for no ground signal from PCM would be low system pressure, high system pressure, or failed hi/lo pressure switch. The hi/lo pressure switch tells the PCM, that it's safe to enable the compressor. You can test the switch w/ VOM. It should show a closed (zero resistance) condition. If not, either system is low on pressure or switch has failed. Pressure switch on your system has two sets of contacts; 2-3 (wht/grn and blk) are for pressure switch B (which should be open). Pressure Switch A contacts 1-4 (blu/red & blue) are the ones which provide feedback to PCM to enable compressor to start. Pressure switch is on pax side and low on the condensor end.

It is unlikely for the compressor coil, compressor, and PCM all to be faulty.

Have they tested the compressor coil and determined it's open, or more likely they want to replace this expensive item to "insure no return",...at your expense. It's a no brainer for them, but a pain in the wallet for you.

Has anyone jumped the compressor relay (provide a ground while disconnecting computer path or simply jumper relay path? This would show if compressor clutch would engage or not to confirm bad clutch coil.

Worst case you can replace all the items yourself and get a shop to charge the AC. You will likely need to have keys reprogrammed.

I don't think you've been served well by the shops you've visited.

good luck

Check car-part.com and ebay for replacement PCM's and compressors (used).

TexasHonda,
I will get after your suggestions on Sunday or Monday and reply back. This is excellent information. Thanks.
Scott

PCM voltage
 

Hello, I am experiencing the same issue with my 2004 Accord V6.

Did you ever figure out the problem?

I have jumpered the hi/low switch and it is broken. But after jumpering it I still have to jumper the relay for the clutch on the compressor. Only after jumpering both together, will the AC run.

The diagnostics I ran points to the PCM not sending the OK signal to the relay. I have made sure the relay works by switching it with a known working one out of another car.

Thanks for any help!

There are some electrical tests you should do before assuming the PCM is the problem.

When you turn on the a/c inside the car with the engine running, do both radiator fans turn on?

There are 4 sockets on the fuse box where the compressor relay plugs in. 2 of the pins should have 12V when the engine is running. Use a good ground like the - battery post or a valve cover bolt for your volt meter ground.

How did you jump the wires on the pressure switch connector? The pressure switch has 4 wires as well. The blu/red and red/grn should have ~5V. The blk wire should have continuity to ground.

The pressure switch is two switches in one part. On the actual switch, pins that correspond to the blu/red to blu should be a closed circuit.

Let us know what you find.

I was able to find a local shop that had a system to reprogram the PCM. I bought a refurb and had them reprogram it for me. I got out by spending only about $1100 which still hurt, but did fix my problems as well as saved me money instead of spending at the dealership. I also ended up trading the car about a year later and it was still running strong but just got a great deal on a new accord.

AC Diagnostics
 

Thank you for the replys. I will try to answer all of your questions today PAhonda. I will have a chance to mess with it today.

Just to give you a full picture of the car, I did just replace the compressor and condenser, and had it charged. I completely overlooked the hi/low sensor which I should have replaced while the system was open. So that's my fault, however I am okay with cutting that out completely if I can. And just splicing together the two wires that need to be closed.

To answer one of your questions I just jumped the hi/low with a paper clip after looking at a diagram of the pins.

More later today.

Thanks again for the help!

AC Diagnostics
 

Okay, I have messed with it today and have some answers for you.

Neither of the Radiator fans turn on with the car running and the AC button on.

2 of the relay pins return 14v while the car is running so that is normal.

Now when I jumper the Blu/red and the Blu wire for the hi/low switch and press the AC button with the car on both radiator fans then run, but the compressor still does not engage the clutch. The clutch will engage manually with a jumper in the relay pins and then the AC blows cold. But once the relay is replaced it will not work. I have used a working relay so I know mine is good.

Thanks again!!